On The Simulation Research Of The MAC Protocols For Underwater Wireless Sensor Network

With the progress in modern information technology, the researches on the wireless sensor network keep the rapid development accordingly. However, due to the non-negligible physical restrictions of the underwater acoustic communication, most MAC protocols applied in the existing wireless sensor network become inapplicable. MAC protocols based on the multiple-access, such as FDMA, TDMA and CDMA, are generally not applicable to the communication requirement in underwater sensor network. The features of underwater wireless sensor network channel, especially the large transmission delay of underwater acoustic channel, make it necessary to reduce or avoid the multiple access conflict in the design of MAC protocols. Therefore, the application of random access MAC protocol by means of the channel reservation mechanism becomes the natural choice for the underwater wireless sensor network. This paper focuses on the simulation analysis of two types of MAC protocols suitable for the underwater wireless sensor network. It is expected that those factors which dominate the performance of MAC protocols in the underwater wireless sensor network could be revealed, thus laid a necessary foundation and basis for the further improved MAC protocol design for the future underwater wireless sensor network.Since MACAW protocol can effectively reduce the channel conflict by using RTS-CTS signaling and can operate even with a heavy network traffic, it could be utilized in underwater wireless sensor network. The thesis studied this classical channel reservation based MAC protocol at first and verified its performance in the environment of underwater wireless sensor network through the OPNET simulation platform. After analyzing and discussing the dominating factors on its achieved performance, the thesis puts forward some preliminary thoughts and methods for its further improvement, which is validated by the simulation. Furthermore, this thesis analyzed another channel reservation based MAC protocol for the underwater wireless sensor network, namely the T-Lohi protocol. Because T-Lohi Protocol can effectively reduce the network delay by simplifing the interaction of channel reservation mechanism, thus reducing the involved time duration. The simulation analysis through OPNET simulation platform also confirms the performance of T-Lohi protocol in the environment of underwater wireless sensor network, the thesis also brought forward some improved method to reduce the network delay, which was validated by the simulation resuls as well.It is shown through the simulation analysis in this thesis that, in the underwater sensor network environment, both the MACAW protocol and the T-Lohi protocol have favorable performance in terms of the packet delivery success ratio, throughout and network delay. More specifically, T-Lohi protocol adopts the way of intercepting the reservation frame to replace RTS-CTS handshake signaling, which can effectively reduce the access conflicts and meanwhile significantly decrease the network access delay. Therefore, T-Lohi protocol outperforms in the aspects of delivery success ratio, throughout and network delay. When considering the improved method for MACAW protocol, this thesis proposed to introduce the extra channel interception mechanism. If the node intercepts that the destination address of RTS frame is not for itself, it will fall asleep. At this moment, the required transmission of upper data will also be cached to be sent in the next round. The simulation results show that the improved MACAW protocol may achieve improvement in delivery success ratio and network throughout as expected owing to the reduction of the multiple access conflict. While for the T-Lohi protocol, this thesis suggests to reduce the reservation time interval. It is shown through the simulation verification that, the proposed improved method can effectively reduce the network delay with small degradation in the packet delivery success ratio.Through the simulation researches on the MACAW protocol and T-Lohi protocol for underwater wireless sensor network, this thesis present some preliminary exploration on the MAC protocol for the underwater wireless sensor network, which would lay a foundation for the further investigation and improved research efforts.